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T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. [1] Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally. (This property holds because T tubules run ...
In skeletal muscle, there is a very high concentration of L-type calcium channels, situated in the T-tubules. Muscle depolarization results in large gating currents, but anomalously low calcium flux, which is now explained by the very slow activation of the ionic currents.
Diagram of sarcoplasmic reticulum with terminal cisternae and T-tubules. Skeletal muscle exhibits a distinctive banding pattern when viewed under the microscope due to the arrangement of two contractile proteins myosin, and actin – that are two of the myofilaments in the myofibrils.
Cardiac and skeletal muscle cells contain structures called transverse tubules (T-tubules), which are extensions of the cell membrane that travel into the centre of the cell. T-tubules are closely associated with a specific region of the SR, known as the terminal cisternae in skeletal muscle, with a distance of roughly 12 nanometers, separating ...
However, cardiac muscle cells contain a diad, which is a linking of only one sarcoplasmic reticulum with its respective t-tubule. Another notable distinction between all muscle cells and cardiac muscle cells is the presence of intercalated discs. These tight connections between the cardiomyocytes allows for the accelerated sending of action ...
(See reference [13] for an illustration of the signaling cascade involving L-type calcium channels in smooth muscle). L-type calcium channels are also enriched in the t-tubules of striated muscle cells, i.e., skeletal and cardiac myofibers. When these cells are depolarized, the L-type calcium channels open as in smooth muscle.
These are known as transverse-tubules (t-tubules); which are also found in skeletal muscle cells and allow for the action potential to travel into the centre of the cell. [7] Special proteins called L-type calcium channels (also known as dihydropyridine receptors (DHPR)) are located on the t-tubule membrane , and are activated by the action ...